Thank you for visiting nature.com. You are using a browser version with
limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off
compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site
without styles and JavaScript.

Subjects

Abstract

The Messinian salinity crisis1,2 (5.96 to 5.33 million years ago) was caused by reduced water inflow from the Atlantic Ocean to the Mediterranean Sea resulting in widespread salt precipitation and a decrease in Mediterranean sea level of about 1.5 kilometres due to evaporation3. The reduced connectivity between the Atlantic and the Mediterranean at the time of the salinity crisis is thought to have resulted from tectonic uplift of the Gibraltar arc seaway and global sea-level changes, both of which control the inflow of water required to compensate for the hydrological deficit of the Mediterranean1,4. However, the different timescales on which tectonic uplift and changes in sea level occur are difficult to reconcile with the long duration of the shallow connection between the Mediterranean and the Atlantic5 needed to explain the large amount of salt precipitated. Here we use numerical modelling to show that seaway erosion caused by the Atlantic inflow could sustain such a shallow connection between the Atlantic and the Mediterranean by counteracting tectonic uplift. The erosion and uplift rates required are consistent with previous mountain erosion studies, with the present altitude of marine sediments in the Gibraltar arc6,7 and with geodynamic models suggesting a lithospheric slab tear underneath the region8,9,10. The moderate Mediterranean sea-level drawdown during the early stages of the Messinian salinity crisis3,5 can be explained by an uplift of a few millimetres per year counteracted by similar rates of erosion due to Atlantic inflow. Our findings suggest that the competition between uplift and erosion can result in harmonic coupling between erosion and the Mediterranean sea level, providing an alternative mechanism for the cyclicity observed in early salt precipitation deposits and calling into question previous ideas regarding the timing of the events that occurred during the Messinian salinity crisis1.

Acknowledgements

We thank P. Meijer, S. Giralt, L. Matenco and C. Ayora for comments and criticisms on earlier versions of the manuscript. This work was funded by the Spanish government through the projects ATIZA (CGL2009-09662), TopoAtlas (CGL2006-05493), TopoMed (CGL2008-03474-E/BTE) and TopoIberia (CSD2006-00041).

Article Tools

Tools

Share

Editorial Summary

The Mediterranean's salinity crisis

About six million years ago, a series of geological factors drastically reduced the exchange of water between the Atlantic Ocean to the Mediterranean Sea through what is now the Strait of Gibraltar. The resulting widespread salt precipitation in the Mediterranean, linked to a decrease in sea level of about 1.5 kilometres due to evaporation, is known as the Messinian salinity crisis. The exact mechanism that caused the crisis remains uncertain. Here Daniel Garcia-Castellanos and Antonio Villaseñor propose a competition between the obstruction of the Gibraltar arc seaway by tectonic uplift and its erosional deepening by water inflow, controlled by the resulting changes in sea-level difference across the Gibraltar arc, as a possible mechanism for the crisis.